FIG. 1 depicts a portion of the conventional disk drive 10. The conventional disk drive includes a carbon layer 14 and underlying substrate 12. For example, the substrate may be part of a slider 12. In addition, other structures may be fabricated on the slider 12. The slider 12 may include structures such as write transducer shields, read transducer shields, dielectric layers or other features not explicitly shown in FIG. 1. In such a case, the carbon layer 14 may be a diamond-like carbon (DLC) layer provided on the ABS of the slider 12. Alternatively, the carbon layer 14 may be a DLC layer on the surface of a disk 12.
Failure analysis is often desired to be performed on the conventional disk drive 10. As part of failure analysis, characteristics of the disk drive 10, particularly those which may contribute to failure or poor operation of the conventional disk drive 10, are investigated. For example, the wear of the conventional carbon layer 14 may be examined. In order to characterize wear and other features of the conventional disk drive 10, the thickness of the carbon layer 14 is desired to be experimentally determined.
FIG. 2 is a flow chart depicting a conventional method 50 for determining the thickness of a carbon layer, such as the carbon layer 14. For simplicity, some steps are omitted. The carbon layer 14 is exposed to light used for Raman spectroscopy, via step 52. Light scattered from the carbon layer 14 is detected and used provide a Raman spectrum, via step 54. Typically, the Raman spectrum includes one or more peaks around frequencies specific to the carbon layer 14. Based on the spectrum, the thickness, d, of the carbon layer 14 is determined, via step 56.
Although the conventional method 50 may be able to determine the thickness for some conventional disk drives 10, there may be drawbacks. Portions of the carbon layer 14 may be thinned due to wear. Although shown as having a single thickness in FIG. 1, the thickness of the carbon layer 14 may actually vary across the slider/disk 12. Further, for current generation disk drives, the carbon layer 14 may be thin. For example, portions of the carbon layer 14 may be less than or equal to twenty-five Angstroms thick. For carbon films that have such a thickness and reside on an AlOTiC slider, the substrate/slider may greatly affect the output signal used for Raman spectroscopy. As a result, conventional Raman spectroscopy using the method 50 may result in large peaks for which noise is a significant component and which provide little information about the carbon layer. Further, transitions between underlying structures, such as shield edges, may affect the intensity of scattered light and thus the Raman spectrum. As a result, determining the thickness of the carbon layer 14 may be difficult or impossible using conventional Raman spectroscopy.
Surface enhanced Raman spectroscopy (SERS) is a technique used in characterizing thin films. In SERS, a film may be deposited on a metal enhancement layer, such as Ag. The underlying metal enhancement layer may allow for an enhanced signal from the film to be characterized. However, in the context of a slider/disk 12, the carbon layer 14 is already deposited. Thus, it may not be possible to place a metal enhancement film under the carbon film to be characterized. Thus, conventional SERS may not be of assistance in characterizing the carbon layer 14. Accordingly, what is needed is an improved method for characterizing a carbon layer of a disk drive, for example on a slider or disk.